From nobody Fri Feb 13 17:31:36 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 36B62E7D0D1 for ; Fri, 22 Sep 2023 06:34:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230132AbjIVGe7 (ORCPT ); Fri, 22 Sep 2023 02:34:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231449AbjIVGer (ORCPT ); Fri, 22 Sep 2023 02:34:47 -0400 Received: from mail-lf1-x136.google.com (mail-lf1-x136.google.com [IPv6:2a00:1450:4864:20::136]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1047883 for ; Thu, 21 Sep 2023 23:34:41 -0700 (PDT) Received: by mail-lf1-x136.google.com with SMTP id 2adb3069b0e04-5041335fb9cso2901584e87.0 for ; Thu, 21 Sep 2023 23:34:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=semihalf.com; s=google; t=1695364479; x=1695969279; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=X0X0BQrsVOxiQjDtIc1DCYhpQrHoUJ1FNBPQ6K4eAiM=; b=SzhoGtdChgxsxHrm+kWRv2zz0g4zFicJwE9TLt1wbSDnfLgRw0DgC88gWkg6OzFM1d qi4o5mWTxjZY11az08COuz/PUl5zmVYOB8g6gcBjtH2h0+h2/zKNbNMSta71pp7L4GYh n22syFjx4iRFVOJUsngVNrhPfuuOB2EgDy+R5ZitWtqxuGWUCHc9D0JPEkHkkLoSV7d+ Rit/MlVLG8JCHqpjcdHTqHIX1QzmEppd5VyqRYlBujfAQEJl/y+hzp5zCdm1RAVLsM0k km8x44FF94DO+F8rZ617L6b5oN/fanOjAQznBy7FC46ZXQwi2vGFsUQbDFrWV+jCgjEE NJ2g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1695364479; x=1695969279; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=X0X0BQrsVOxiQjDtIc1DCYhpQrHoUJ1FNBPQ6K4eAiM=; b=uMuYXsUt+LWQuPtlGlhyrwXjRqGe/DZFfma+Jiwv+X965vh5OLRe0DVUK5ehVKX84Z 5MHCYZQylGGWtSe25KzwIG43t2/g3WMOx5EcruBWEfiyQcbNfqwWuPBpcikYy1ZK/vCJ tqTNlnb6/5B5hbityTtquI3/QiXLQA1JHvcqV/aE78o/idX3TL+E6T2srThBOIcCCE3+ YCs6RlyM8G6X06gp6HbhOp4p03qnOVvc6nKrGUl59fBOG2vAB4ZIQw5V1DfRZwx+eFNP 9O9xXLJO1bi4+2GANIp7LO2w2elleTLgHr4LfUhQnVlFPEtPJZxzPtWw50XTSFZBZwop a86A== X-Gm-Message-State: AOJu0YwM/itF/nwuIGMQlCzvEUVsxVu5ROHyhDUci4IW9ryNBuGvwj9z Mo92efCxVCdHjQPB46va+iO8GBsaFdYauT1YV6Y= X-Google-Smtp-Source: AGHT+IHIBbiTE5xvp6VdZFE5vYOK4NhSyuG2r1s6YRy3GBiGfUmu9KZWjlhVbjMROpC6z3Eo5K9uMg== X-Received: by 2002:a19:5057:0:b0:503:2561:c8b with SMTP id z23-20020a195057000000b0050325610c8bmr6555667lfj.33.1695364479071; Thu, 21 Sep 2023 23:34:39 -0700 (PDT) Received: from lmajczak1-l.roam.corp.google.com ([83.142.187.84]) by smtp.gmail.com with ESMTPSA id w29-20020a05651204dd00b00502a96484absm612105lfq.99.2023.09.21.23.34.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 21 Sep 2023 23:34:38 -0700 (PDT) From: Lukasz Majczak To: David Airlie , Daniel Vetter Cc: Radoslaw Biernacki , Guenter Roeck , upstream@semihalf.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Lukasz Majczak , stable@vger.kernel.org Subject: [PATCH v3] drm/dp_mst: Fix NULL deref in get_mst_branch_device_by_guid_helper() Date: Fri, 22 Sep 2023 08:34:10 +0200 Message-ID: <20230922063410.23626-1-lma@semihalf.com> X-Mailer: git-send-email 2.42.0.515.g380fc7ccd1-goog In-Reply-To: <20230921131201.157767-1-lma@semihalf.com> References: <20230921131201.157767-1-lma@semihalf.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" As drm_dp_get_mst_branch_device_by_guid() is called from drm_dp_get_mst_branch_device_by_guid(), mstb parameter has to be checked, otherwise NULL dereference may occur in the call to=20 the memcpy() and cause following: [12579.365869] BUG: kernel NULL pointer dereference, address: 0000000000000= 049 [12579.365878] #PF: supervisor read access in kernel mode [12579.365880] #PF: error_code(0x0000) - not-present page [12579.365882] PGD 0 P4D 0 [12579.365887] Oops: 0000 [#1] PREEMPT SMP NOPTI ... [12579.365895] Workqueue: events_long drm_dp_mst_up_req_work [12579.365899] RIP: 0010:memcmp+0xb/0x29 [12579.365921] Call Trace: [12579.365927] get_mst_branch_device_by_guid_helper+0x22/0x64 [12579.365930] drm_dp_mst_up_req_work+0x137/0x416 [12579.365933] process_one_work+0x1d0/0x419 [12579.365935] worker_thread+0x11a/0x289 [12579.365938] kthread+0x13e/0x14f [12579.365941] ? process_one_work+0x419/0x419 [12579.365943] ? kthread_blkcg+0x31/0x31 [12579.365946] ret_from_fork+0x1f/0x30 As get_mst_branch_device_by_guid_helper() is recursive, moving condition to the first line allow to remove a similar one for step over of NULL eleme= nts inside a loop. Fixes: 5e93b8208d3c ("drm/dp/mst: move GUID storage from mgr, port to only = mst branch") Cc: # 4.14+ Signed-off-by: Lukasz Majczak Reviewed-by: Radoslaw Biernacki --- v2->v3: * Fixed patch description. drivers/gpu/drm/display/drm_dp_mst_topology.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/dr= m/display/drm_dp_mst_topology.c index ed96cfcfa304..8c929ef72c72 100644 --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c @@ -2574,14 +2574,14 @@ static struct drm_dp_mst_branch *get_mst_branch_dev= ice_by_guid_helper( struct drm_dp_mst_branch *found_mstb; struct drm_dp_mst_port *port; =20 + if (!mstb) + return NULL; + if (memcmp(mstb->guid, guid, 16) =3D=3D 0) return mstb; =20 =20 list_for_each_entry(port, &mstb->ports, next) { - if (!port->mstb) - continue; - found_mstb =3D get_mst_branch_device_by_guid_helper(port->mstb, guid); =20 if (found_mstb) --=20 2.42.0.515.g380fc7ccd1-goog